What marketers need to know about server-side tracking

Server-side tracking offers a number of benefits: Web page loading time can be improved, dependency on cookies can be reduced, data quality and privacy compliance can be increased.

Thus, server-side tracking seems to be the solution for maximizing data volume. But is this true?

The focus here is on these three key issues:

  1. US data transfer: The legality of the transfer of personal data to the USA stands and falls with the validity of the EU-US data privacy framework. If only anonymised data is processed, the problem does not apply.
  2. Tracking blockers: 10 to 20 percent of users install browser extensions such as Ghostery or Adblock Plus.  However, calls from custom domains are not blocked.
  3. Cookie restrictions: 3rd party cookies are completely blocked by many browsers and 1st party cookies set on the client side by tracking services are limited to a maximum of 7 days. Excluded from Intelligent Tracking Protection (ITP) are server-side 1st party cookies.

Let’s take a closer look.

Client-side versus server-side web analysis method

Classic web analytics is based on the client-side tracking method. Implementation is comparatively simple thanks to tag management solutions or integrated tag management functions of individual services.

Today ensuring a sufficient database and reliable data quality is a major challenge for marketers. This is because a large part of the data can be lost or distorted due to tracking protection measures and the legal obligation of consent according to the GDPR and TTDSG.

client-side Web Tracking

The principle of server-side tracking is that a direct connection between the users’ device and the actual tracking services is avoided and the data is anonymized or pseudonymized before being passed on.

server-side Web Tracking (Ideal)

However, here consent management can also only be dispensed with if no data such as the screen resolution is read from the end device and no cookies are set for statistical or marketing purposes, and complete anonymization takes place before forwarding or storage. The server-side Google Tag Manager, for example, records the screen resolution by default and always requires prior consent for this reason alone.

In addition, the 1st party server may not be operated in an environment (cloud) that is managed by a provider from the USA, even if the servers are located in a European data center. This is because even the process of anonymization is data processing according to the GDPR. This means that infrastructure providers such as Google, AWS, Azure and Cloudflare are likely to be excluded.

Ideal versus reality

If you look behind the facade of the promises of salvation for server-side tracking, the challenges quickly become apparent. And these challenges are not limited to the complex technical implementation:

1. Even client-side 1st party cookies that are not absolutely necessary require consent. It does not matter whether, among others, necessary purposes are pursued. Necessity must always be assessed from the user’s point of view and not in terms of more convenient integration or configuration for the marketer. And once consent is required, much of the data is lost and the rest can be heavily skewed, as consent rates usually vary by channel and campaign.

2. The thing with the complete anonymization of the data is not so easy to implement in practice. Only anonymization of the IP address is definitely not sufficient!

The Court of Justice of the European Union requires that a re-identification of the data subjects by the data recipients must not be practically feasible (ECJ, judgment v. 26.04.23, AZ: T 557/20). For this purpose, all client or device, user and session IDs, in particular of the marketing platforms, must be deleted or transformed. It is possible that the user agent and a timestamp are already sufficient for Google and Meta to identify a natural person. Google signals must not be activated under any circumstances, as this results in a link to the Google accounts of the users and thus naturally makes it possible for Google to identify the data recipient.

With the server-side Google Tag Manager, data can be transformed, but only to a limited extent, so that complete anonymization is not possible. This is shown by a comparison of the data in the transformation settings:

3. Complete anonymization of data is accompanied by significant functional limitations, up to and including complete inability to function. Without Google Signals, no information on age, gender and interests is provided. Without user IDs, remarketing is also not possible. The idea that marketing tools can simply be reused is therefore a myth.

Client-side versus server-side conversion tracking

Instead of setting up the entire web analytics on the server side, it is also possible to manage only the exchange with the marketing platforms for conversion tracking via a server-side exchange.

With server-side conversion tracking, only minimal, precisely defined data sets are uploaded to US advertising platforms. As a rule, only click IDs are used as identifiers, which only allow mapping to campaigns, but not to individual users, and therefore do not fall under personal data and thus avoid the problems with the US data transfer.

This means that marketers can continue to control and optimize bids on the basis of conversions or sales. Tools such as Google Ads can be used as usual. The conversion upload to the marketing platforms can be automated daily after a one-time setup.

The use of conversion tags by Google, Meta & Co. is currently illegal due to the US transfer issue. Even if a new EU-US agreement were to be reached that would be valid, there would still be a general obligation of consent. This means that conversions would only ever be measured after consent has been given, as the legitimate interests of the data subjects would prevail in data processing. Depending on the consent rate, 50 – 80% of the conversion information is lost as a result. Furthermore, the measured conversions are usually distorted and thus misleading, as consent rates usually vary greatly between channels and campaigns. Additionally, ad and tracking blockers lead to further data loss. And last but not least, Apple’s Intelligent Tracking Protection puts a stop to customer journey tracking by limiting the cookie lifetime to 24 hours for ads, regardless of consent.

With server-side conversion tracking, all these limitations can be avoided and reliable data quality can be ensured. As a result, the optimization algorithms of the platforms receive sufficient and unbiased data, which ensures efficient advertising control.

Hybrid server- and client-side tracking

Completely server-side anonymous tracking is hardly possible in practice. At the same time, ensuring data quality in times of content-related data loss, tracking blocking and browser protection measures is an elementary challenge for data-driven marketing.

It’s all in the mix: In the combination of content-independent cookie-less and privacy-friendly client-side session tracking and server-side conversion tracking, all these challenges can be mastered easily and sustainably.

All visits and conversions can be recorded thanks to the exemption from the consent requirement. When using a custom tracking domain, this also includes protection against tracking blocking. In addition, 1st party cookies are set on the server side with consent.

Hybrid server- & client-side Web Tracking

The automatically anonymized conversion data can be transferred to US marketing platforms without hesitation, as can reporting data in US solutions such as Looker Studio or Power BI.

Setting up server-side conversion tracking

To set up server-side conversion tracking in etracker Analytics for Google Ads, you only need to perform the following steps:

  1. Install tracking code for etracker Analytics manually or via plugin.
  2. If necessary, create individual conversion actions that are not recorded via auto tracking (e.g. via CSS selector events without coding).
  3. Copy & paste suffix parameters to Google Ads campaigns.
  4. Set up Google Ads upload once by creating the conversion action(s) and storing the individual upload URL from the etracker Analytics account.



Server-side conversion tracking is an advanced method to optimize tracking for Google Ads & Co. It increases data quality and avoids legal risks by directly connecting US services. The implementation is done in a few minutes and affordable from 29 Euro per month even for the smallest websites.

Further information

Documentation on conversion upload

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